Apparatus for securing a sensor to a surgical instrument for use in computer guided orthopaedic surgery

ABSTRACT

A self-centering coupling device is provided for coupling a sensor array to a surgical instrument for use in computer guided surgery. The self-centering coupling device includes a sensor support having a stem and sensor support arms coupled to the stem to support the sensors of the sensor array. The self-centering coupling device is received within a recess formed in the surgical instrument.

This is a divisional application of copending U.S. patent applicationSer. No. 10/828,778, which was filed on Apr. 21, 2004, the entirety ofwhich is hereby incorporated by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to a sensor used in computerguided orthopaedic surgery, and more specifically to coupling devicesuse in computer guided orthopaedic surgery.

BACKGROUND

Many computer guided orthopaedic surgical procedures are based ondetermining the position of bones, and relating this position into thecomputer via some type of ultrasonic, magnetic resonance, or opticalsensor. A similar sensor is attached or contained within the surgicalinstrument and subsequently guided via a computer into the desiredposition within the patient. U.S. Patents and Patent Publicationsrelating to computer guided surgery include U.S. Pat. No. 5,520,694 andU.S. Patent Application Publication Nos. 2003/0153978 A1 and2003/01538829 A1, each of which is hereby incorporated by reference.Similar computer guided navigation systems are disclosed in U.S. Pat.Nos. 6,514,259; 6,434,507; 6,428,547; 6,424,856; 6,351,659; 6,223,067;6,187,018; 6,178,345; 5,889,834; 5,769,861; 5,702,406; 5,643,268; and5,628,315, along with U.S. Patent Application Publication No.2002/0038118 A1, each of which is hereby incorporated by reference. Theaccuracy of this guidance is dependent on various factors including, forexample, computer hardware and software resolution, the location of thesensor on the surgical instrument, and manufacturing tolerances of thesensor and its attachment mechanism to the surgical instrument.

Tight manufacturing tolerances often result with increased cost of theattachment mechanism and require precise alignment of the componentsbefore assembly. This may decrease the user-friendliness of theoperation of the attachment mechanism. In an operating room environment,for example, and particularly with the advent of minimally invasivesurgery, the maneuvering space available to the surgeon becomesincreasingly smaller. Precise alignment of tightly machined componentshaving small tolerances may be difficult.

SUMMARY

The present disclosure comprises one or more of the features recited inthe appended claims or one or more of the following features orcombinations thereof.

According to one aspect of the present disclosure, a self-centeringcoupling device is used for securing a sensor to a surgical instrumentfor use in computer guided orthopaedic surgery. The device includes asensor support having a support arm to support the sensor and a stemhaving a first end secured to the support arm. A second end of the stemis expandable between a first position in which the second end of thestem has a first width and a second position in which the second end ofthe stem has a second, larger width.

The device may further include a pin or fastener to secure the sensorsupport to the surgical instrument. The pin moves the second end of thestem from the first position to the second position. According to oneillustrative embodiment, the stem includes a passageway defined by aninner sidewall. The inner sidewall is tapered at the second end of thestem. Insertion of the pin into the passageway causes the second end ofthe stem to be moved from the first position to the second position.

According to another aspect of the present disclosure, the sensorsupport is constructed with a polymeric material. In one illustrativeembodiment, the sensor support is constructed with a polycarbonateplastic.

According to yet another aspect of the present disclosure, a surgicalinstrument used in computer guided orthopaedic surgery includes a bodyhaving a recess configured to receive a sensor support. The recess isdefined by a first side wall, a second side wall, and a bottom wall. Thefirst side wall and the second side wall are inclined relative to oneanother. The recess is further defined by a third side wall and a fourthside wall such that the third and fourth side walls are inclined alsorelative to one another. The first side wall and the second side wallare arranged in a substantially V-shaped configuration and the thirdside wall and the fourth side wall are arranged in a substantiallyV-shaped configuration.

According to still another aspect of the present disclosure, a method ofattaching a sensor support carrying a sensor array to a surgicalinstrument for use in computer guided orthopaedic surgery includespositioning an end of the sensor support into a recess formed in thesurgical instrument and inserting a pin into a passageway of the sensorsupport to urge outer walls of the sensor support to contact with anumber of side walls of the recess.

According to yet another aspect of the present disclosure, a method ofusing a computer guided orthopaedic surgical instrument includesremoving a first sensor support from a first sterile package, securingthe first sensor support to the surgical instrument with a sterilefastener, performing a first computer guided orthopaedic surgicalprocedure, removing the fastener and the first sensor support from thesurgical instrument, disposing of the first sensor support, sterilizingthe fastener for use in a second computer guided surgical procedure,removing a second sensor support from a second sterile package, securingthe second sensor support to the surgical instrument with the fastener,and performing a second computer guided orthopaedic surgical procedure.

The above and other features of the present disclosure will becomeapparent from the following description and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a portion of an orthopaedic broachhaving a sensor array coupled to the broach by a self-centering couplingdevice;

FIG. 2 is an exploded, perspective view of the self-centering couplingdevice of FIG. 1;

FIG. 3 is a bottom view of the sensor support of the self-centeringcoupling device of FIG. 1;

FIG. 4 is a sectional view of the sensor support taken along line 4-4 ofFIG. 3;

FIG. 5 is a front view, with portions broken away, of a pin of theself-centering coupling device;

FIG. 6 is a sectional view taken along line 6-6 of FIG. 3 showing thesensor support positioned within a recess of the surgical instrument andshowing the pin being inserted into the passageway of the stem of thesensor support;

FIG. 7 is a sectional view similar to FIG. 6 showing the fastenerinserted farther within the passageway of the sensor support;

FIG. 8 is sectional view similar to FIGS. 6 and 7 showing the threadedscrew of the pin threaded into the threaded bore of the recess formedwithin the surgical instrument;

FIG. 9 is a sectional view taken along line 9-9 of FIG. 6; and

FIG. 10 is a sectional view similar to FIG. 9 that is taken along line10-10 of FIG. 8.

DETAILED DESCRIPTION OF THE DRAWINGS

A self-centering coupling device 10 is used to attach a computer-guidedsensor array 12 onto a surgical instrument such as a broach handle 14,shown in FIG. 1, for example. The self-centering coupling device 10 isreceived into a generally diamond-shaped recess 16 formed in the broachhandle 14 (as shown in FIG. 2). The device 10 includes a sensor support18 that supports spherical sensors 20 of sensor array 12 and a fasteneror pin 22 that couples the sensor support 18 to the surgical broachhandle 14. In general, the sensor array 12 and the coupling device 10are used during computer guided orthopaedic surgical procedures. Thesensor array 12, when coupled to the broach handle 14 shown in FIG. 2,is used by a navigation system to track the position of the broachhandle 14 during surgery. Although herein described in regard to abroach handle, the self-centering coupling device 10 may be used tosupport the sensor array 12 on or any other type of surgical instrumentused during computer guided orthopaedic surgery or other surgicalprocedures as well.

Looking now to FIG. 2, the sensor support 18 includes a stem 30 having afirst or distal end 32 and a second or proximal end 34. First, second,and third sensor support arms 36 are each coupled to the distal end 32of stem 30. Each sensor support arm 36 includes an arm portion 38 and athreaded shaft 40 coupled to an outer end of the arm portion 38.Illustratively, each spherical sensor 20 includes a threaded bore 41formed to receive the threaded shaft 40 of one of the sensor supportarms 36 in order to couple each sensor 20 to the sensor support 18. Thesensors 20 may be ultrasonic, magnetic resonance, or optical sensors,for example. Sensors 20 are commercially available from BrainLAB AG ofHeimstetten, Germany.

The stem 30 of the sensor support 18 includes a generally cylindricalouter wall 42 defining a passageway 44 between distal end 32 andproximal end 34. As shown in FIG. 4, a proximal end portion ofpassageway 44 is tapered and is shown to narrow at the proximal end 34of the stem 30. As is discussed in greater detail below, the walls ofpassageway 44 are engaged by pin 22 to expand the proximal end 34 of thestem 30 outwardly when the pin 22 is inserted through the passageway 44and engages the narrowed, proximal end portion of passageway 44.

The stem 30 of the sensor support 18 further includes first and secondlongitudinal slots 50, 52 formed in outer wall 42, as shown in FIGS. 2and 4. Illustratively, slots 50, 52 extend from the proximal end 34 ofthe stem 30 toward the distal end 32 and are parallel to a vertical axis54 defined along a length of the stem 30. Slots 50, 52 are positionedapproximately 180° apart from each other about vertical axis 54 asviewed in FIG. 3, for example, and extend from the proximal end 34 ofstem 30 toward the distal end 32 of stem 30 approximately a distanceless than half a length of stem 30.

Slots 50, 52 cooperate to define first and second outer wall portions56, 58 of outer wall 42. As is discussed in greater detail below, outerwall portions 56, 58 are movable between a first position shown in FIGS.3 and 9 where the slots 50, 52 have a first width 60 at the proximal end34 of stem 30, and a second position shown in FIG. 10 where the slots50, 52 have a second width 62 at the proximal end 34 of stem 30. Thesecond width 62 is greater than the first width 60 such that the ends ofthe outer wall portions 56, 58 are positioned a greater distance awayfrom each other (as viewed from the bottom of sensor support 18) therebyengaging the side walls of recess 16. Note that the opening defined bypassageway 44 at the proximal end 34 of stem 30 increases in size in asimilar manner as slots 50, 52 when the pin 22 is inserted withinpassageway 44.

Further, proximal end 34 of stem 30 has a first width, 63, when stem 30is in the first position, as shown in FIG. 9, and a second width, 65,when stem 30 is in the second position, as shown in FIG. 10. Secondwidth, 65, is greater than first width, 63. As shown in FIGS. 9 and 10,first and second widths, 63 and 65, are illustratively taken through acenter of stem 30. However, a width taken between any two oppositepoints of the proximal end 34 of the stem 30 increases as proximal end34 of stem 30 is moved from the first position to the second position.

As is discussed in greater detail below, insertion of the pin 22 intothe passageway 44 of the stem 30 expands the proximal end 34 of the stem30 of the sensor support 18 by urging outer wall portions 56, 58outwardly away from one another. The diameter of the tapered portion ofpassageway 44 is smaller than the diameter of the pin 22 inserted inpassageway 44 such that the pin 22 acts against an inner surface or sidewall 64 of the tapered portion of passageway 44 (defined by outer wallportions 56, 58) to move outer wall portions 56, 58 to their expandedpositions.

Looking now to FIGS. 2 and 6-8, stem 30 of sensor support 18 furtherincludes anti-backout catches or tabs 66, 68. Each tab 66, 68 is formedby a generally “U-shaped” slot 70 formed in outer wall 42 of stem 30such that each tab 66, 68 is anchored to outer wall 42 at one end andmovable relative to the outer wall 42 at the other end. Each tab 66, 68further includes a lip 72 extending inwardly into the passageway 44 ofstem 30. As is discussed below, the lip 72 of each tab 66, 68 engages aportion of the pin 22 as the pin 22 is inserted into the passageway 44.The tabs 66, 68 operate as anti-backout catches or tabs to maintain thepin 22 within the passageway 44 and to prevent the pin 22 fromunintentionally being removed from within the passageway 44 onceinserted.

Sensor support 18 further includes a generally teardrop-shaped foot 100formed by a lobe 101 at the proximal end 34 of stem 30. Foot 100includes a portion of each outer wall portion 56, 58, as shown in FIGS.2, 9, and 10. As is discussed below, foot 100 allows a user to key orotherwise properly orient the sensor support 18 in a certain positionwith respect to the broach handle 14 when coupling the sensor support 18to the broach handle 14. Each sensor 20 of the sensor array 12 is to beoriented or positioned in a particular manner in order to relay theproper position of the broach 14, to which the sensors 20 are attached,back to the main computer, for example. The foot 100 of the sensorsupport 18, therefore, allows the user to quickly and easily orient thesensor support 18 (and sensor array 12 thereon) in the proper position.

Illustratively, sensor support 18 is made by injection molding apolymeric material into a mold. The disclosure herein, however, is notlimited by the injection molding process. In a specific exemplaryembodiment, sensor support 18 is made from polycarbonate plastic. Othersuitable plastics, such as polyethylene or high density polyethylene,for example may be used as well. For example, the sensor support 18 maycomprise a plastic selected from the group consisting of acrylic, epoxy,polyester, polypropylene, polyurethane, polyethylene, polycarbonate,polystyrene, polysulfone, polyetherimide, polyethersulfone,polyphenylsulfone, polyphenylsulfide, acrylonitrile-butadiene-styrenepolymer, polyetheretherketone, and combinations thereof. It should beappreciated that other types of thermosetting or thermoplastic resinsmay be used to fit the needs of a given design. Because sensor support18 is made of a plastics material and is able to be mass produced byinjection molding, for example, a generally low cost and disposabledevice is able to be produced. Further, the disposability of the sensorsupport 18 provides that the sensor support 18 does not need to berecalibrated after every use.

As shown in FIG. 5, pin 22 includes a top or head portion 74, a plunger76 coupled to head portion 74, and a bottom or foot portion 78. Footportion 78 includes a central cavity 80 formed to receive the plunger76. A spring 82 is also positioned in the cavity 80 about plunger 76. Asshown in FIG. 5, a first end of spring 82 is engaged with a bottomsurface 75 of head portion 74 while a second end of spring 82 is engagedwith an inner, bottom surface 77 of foot portion 78 to bias the headportion 74 and foot portion 78 in a direction away from one another.

Pin 22 further includes an outer rim 84 coupled to head portion 74. Asshow in FIGS. 6-8, outer rim 84 passes tabs 66, 68 as pin 22 is insertedinto passageway 44 of stem 30. As outer rim 84 passes tabs 66, 68, tabs66, 68 are urged to move outwardly away from each other, as shown inFIG. 7. Once pin 22 is inserted within passageway 44 to a position wherethe outer rim 84 is positioned below the tabs 66, 68, the lip 72 of eachtab 66, 68 helps to maintain the pin 22 within the passageway 44. Forexample, the outer rim 84 of the pin 22 engages the lip 72 of each tab66, 68 thereby providing resistance to upward movement of the pin 22through the passageway 44.

A threaded screw 69 of pin 22 is coupled to a proximal end of theplunger 76. Threaded screw 69 extends past a bottom wall 71 of footportion 78 of pin 22, as shown in FIGS. 6-8. Further, foot portion 78includes a tapered portion 73 at a proximal end of pin 22.Illustratively, the fastener 22 is made from a metal material such as acobalt-chrome alloy. However, the pin 22 may be made from other suitablematerials such as a plastic, for example.

Looking now to FIGS. 2, 9, and 10, recess or receiver 16 is formedwithin broach handle 14. Recess 16 may, however, be formed within anysurgical instrument intended for use during computer guided orthopaedicsurgery. Recess 16 is generally diamond-shaped or tear-drop shaped andis defined by a first pair of opposite, inclined surfaces or side walls86, 88 which generally form a “V-shape” and a second pair of opposite,inclined surfaces or side walls 90, 92 which also generally form a“V-shape”. The first pair of side walls 86, 88 each have a first lengthand the second pair of side walls 90, 92 each have a second lengthlonger than the first length. Illustratively, as shown in FIGS. 9 and10, the V-shape of each pair of side walls 86, 88 and 90, 92 is rounded.Recess 16 is further defined by a bottom wall 94 formed in broach handle14 and coupled to each side wall 86, 88, 90, 92. A threaded bore 95 ofrecess 16 is formed through bottom wall 94 of recess 16, as shown inFIGS. 6-8. Threaded bore 95 is provided to receive threaded screw 69 ofpin 22 therein. Although a threaded bore 95 and corresponding threadedscrew 69 are provided, other suitable fasteners or couplers such as aball-plunger activated quick-connect coupler, for example, may be usedas well.

In use, the sensor support 18 may be sterilized and provided in asterilized package (not shown). In preparation for the computer guidedorthopaedic surgery, a surgeon or other member of the surgical teamremoves the sensor support 18 from the sterile package. The user thensecures the sensor support 18 to the surgical instrument to be usedduring the computer guided orthopaedic surgery, such as the handle 14 ofa broach, for example.

To secure the sensor support 18 to the handle 14, the foot portion 100of the stem 30 is positioned within recess 16. Illustratively, theelongated tear-drop shaped portion of foot portion 100 is positionedbetween the second pair of longer side walls 90, 92 defining recess 16such that sensor support 18 is oriented properly with respect to thebroach handle 14. As mentioned above, foot portion 100 of stem 30 actsas a key and cooperates with the elongated diamond-shaped recess 16 toprovide a single orientation of the sensor support 18 with respect tothe broach handle 14.

Once sensor support 18 is properly positioned within recess 16, the pin22 is inserted within the passageway 44, which is tapered at theproximal end 34 of the stem 30 of the sensor support 18, as shown inFIGS. 6-8, for example. Looking first at FIGS. 6 and 9, prior to pin 22having been inserted completely into passageway 44, a small space or gap110 is provided between the proximal end 34 of stem 30 and therespective side walls 86, 88, 90, 92 of recess 16. This excess space, orgap 110 allows stem 30 to be quickly and easily inserted into recess 16.Oftentimes, for example, tight tolerances may hinder a user's ability toquickly and efficiently connect two components together. The additionalspace or gap 110 provided with the current self-centering couplingdevice 10 of the present disclosure, therefore, provides a device thatis easy to assemble and disassemble.

As pin 22 is inserted further into passageway 44, the tapered end 73 ofthe pin 22 enters the tapered portion of passageway 44 at the proximalend 34 of the stem 30, as shown in FIG. 7, for example. The diameter ofthe foot portion 78 of the pin 22 is greater than a diameter of thenarrowed, tapered portion of passageway 44. Therefore, as the footportion 78 enters the tapered portion of the passageway 44, the proximalend 34 of the stem 30 is expanded or otherwise urged outwardly.Specifically, the outer wall portions 56, 58 of the proximal end 34 ofthe stem 30 are urged away from each other from the position shown inFIG. 9 to the position shown in FIGS. 10 and 8. As the outer wallportions 56, 58 are moved outwardly, the gap 110 between the outersurface of the outer wall portions 56, 58 and the side walls 86, 88, 90,92 of recess 16 is reduced and eventually closed. As shown in FIG. 10, aportion of first outer wall portion 56 of stem 30 engages side walls 86,88 of recess 16, and a portion of second outer wall portion 58 of stem30 engages side walls 90, 92 of recess 16.

This process of expanding the proximal end 34 of stem 30 to the point atwhich the outer wall 42 of the proximal end 34 of the stem 30 engagesthe side walls 86, 88, 90, 92 of recess 16 operates to center the stem30 (and thus the entire sensor support 18) within the recess 16. Theself-centering coupling device 10 enables a user to easily andrepeatably position the sensors 20 (mounted on the sensor support 18) insubstantially the same location on the surgical instrument. Once pin 22has been fully inserted into passageway 44, the user then rotates thepin 22 to thread the screw tip 69 of pin 22 into the threaded bore 95 ofrecess 16, as shown in FIG. 8. As pin 22 is rotated in a lockingdirection and as screw 69 is threaded farther into bore 95, foot portion78 of fastener 22 engages the bottom wall 94 of recess 16 and actsagainst the bias of spring 82 to move foot portion 78 and head portion74 toward each other thereby reducing and/or minimizing the gap betweenfoot portion 78 and head portion 74, as shown in FIG. 8.

Once the sensor stem 30 has been coupled to the broach handle 14 by thefastener 22, the sensor array 12 may be coupled to the sensor stem 30.As discussed above, each spherical sensor 20 is coupled to acorresponding threaded shaft 40 of one of the sensor support arms 36.The sensor array 12 may also be coupled to the sensor stem 30 prior tothe sensor stem 30 being inserted into recess 16 formed in broach handle14. At this point the surgeons and other technicians may perform acomputer guided orthopaedic surgical procedure using the broach handle14, for example, to which the self-centering coupling device 10 has beencoupled.

Once the procedure is completed, the pin 22 and the sensor support 18are removed from the broach handle 14. The sensor support 18 and thesensor array 12 coupled to the first sensor support 18 are disposableand may be discarded after the surgical procedure is completed. Asmentioned above in certain embodiments, sensor support 18 is made of apolymeric material, specifically a polycarbonate plastic, and maytherefore be used as a one-use, disposable product. However, the sensorsupport 18 and/or the sensor array 12 may also be re-sterilized and usedagain for a second computer guided surgical procedure. In anillustrative embodiment, the sensor support 18 is disposed after theprocedure, with pin 22 (and perhaps the sensor array 12) beingsterilized and reused. As such, prior to a subsequent computer guidedorthopaedic surgical procedure, for example, a replacement sensorsupport 18 may be removed from a sterile package (not shown) and coupledto a surgical instrument using the sterilized pin 22 that was reclaimedand sterilized from the previous procedure.

1. A method for attaching a sensor support carrying a sensor array to asurgical instrument for use in computer guided orthopaedic surgery, themethod comprising the steps of (a) positioning an end of the sensorsupport into a recess formed in the surgical instrument, and (b)inserting a pin into a passageway of the sensor support to urge outerwalls of the sensor support into contact with a number of side walls ofthe recess.
 2. The method of claim 1, wherein the inserting stepincludes urging the pin into a tapered end of the passageway.
 3. Themethod of claim 1, wherein the inserting step includes threading a screwtip of the pin into a threaded bore of the surgical instrument.
 4. Amethod of using a computer guided orthopaedic surgical instrument, themethod comprising the steps of (a) removing a first sensor support froma first sterile package, (b) securing the first sensor support to thesurgical instrument with a sterile fastener, (c) performing a firstcomputer guided orthopaedic surgical procedure, (d) removing thefastener and the first sensor support from the surgical instrument, (e)disposing of the first sensor support, (f) sterilizing the fastener foruse in a second computer guided surgical procedure, (g) removing asecond sensor support from a second sterile package (h) securing thesecond sensor support to the surgical instrument with the fastener, and(i) performing a second computer guided orthopaedic surgical procedure.5. The method of claim 4, wherein the disposing step comprises disposingof the first sensor support without removing a number of sensorstherefrom.
 6. The method of claim 4, wherein: the disposing stepcomprises removing a number of sensors from the sensor support prior todisposal of the sensor support, and the step of securing the secondsensor support to the surgical instrument comprises securing the numberof sensors to the second sensor support.
 7. The method of claim 6,further comprising the step of sterilizing the number of sensors priorto being secured to the second sensor support.
 8. The method of claim 4,wherein: the step of securing the first sensor support to the surgicalinstrument comprises inserting a pin into a tapered passageway of thefirst sensor support.